For various logistical and technical reasons, concrete floors are typically made up of a series of individual concrete blocks or slabs. The interface where one concrete block or slab meets another concrete block or slab is typically called a joint. Freshly poured concrete shrinks considerably as it hardens due to the chemical reaction that occurs between the cement and water (i.e., hydration). As the concrete shrinks, tensile stress accumulates in the concrete. Therefore, the joints need to be free to open and thus enable shrinkage of each of the individual concrete blocks or slabs without damaging the concrete floor.
The joint openings, however, create discontinuities in the concrete floor surface, which can cause the wheels of a vehicle (such as a forklift truck) to impact the edges of the concrete blocks or slabs which form the joint and chip small pieces of concrete from the edge of each concrete block or slab, particularly if the joint edges are not vertically aligned. This damage to the edges of concrete blocks or slabs is commonly referred to as joint spalling. Joint spalling often interrupts the normal working operations of many facilities by slowing down forklift and other truck traffic, and/or causing damage to trucks and the carried products. Severe joint spalling and uneven joints can cause loaded forklift trucks to overturn (which of course is dangerous to people in those facilities). Joint spalling can also be very expensive and time consuming to repair.
Joint edge assemblies that protect such joints between concrete blocks or slabs are widely used in the construction of concrete floors (such as concrete floors in warehouses). Examples of known joint edge assemblies are described in U.S. Pat. Nos. 6,775,952 and 8,302,359. Various known joint edge assemblies enable the joint edges to both self-open with respect to the opposite joint edge as the adjacent concrete slabs shrink during hardening.
One known joint edge assembly is generally illustrated in FIGS. 1, 2, 3, and 4. This known joint edge assembly 10 includes two separate elongated joint edge members 20 and 40 temporarily held together by a plurality of connectors 60. The connectors 60 connect the elongated joint edge members 20 and 40 along their lengths during installation. This known joint edge assembly 10 further includes a plurality of anchors 22 that extend from the elongated joint edge member 20 into the region where the concrete of the first slab 90 is to be poured such that, upon hardening of the concrete slab 90, the anchors 22 are cast within the body of the concrete slab 90. This known joint edge assembly 10 further includes a plurality of anchors 42 that extend from the elongated joint edge member 40 into the region where the concrete of the second slab 96 is to be poured such that, upon hardening of the concrete slab 96, the anchors 42 are cast within the body of the concrete slab 96. This known joint edge assembly is positioned such that the ends or edges of the concrete slabs are aligned with the respective outer surfaces of the elongated joint edge members. FIGS. 1 and 2 illustrate the joint edge assembly 10 prior to installation and before the concrete is poured, and FIG. 3 illustrates the joint edge assembly 10 after installation and after the concrete slabs have started shrinking such that the elongated joint edge members 20 and 40 have separated to a certain extent.
One known problem with this type of known joint edge assembly is that the joint will open too much or too wide as generally shown in FIG. 4 such that the elongated joint edge members 20 and 40 have separated to a greater extent than that shown in FIG. 3. The distance X between the facing sides of the elongated joint edge members 20 and 40, which is the same distance between the facing sides of the concrete slabs 90 and 96 as shown in FIG. 4, can be up to approximately 31.75 millimeters (approximately 1.25 inches) for certain installations. Such wider joints create many problems.
One problem with such wider joints is that as the joint becomes wider, the joint allows more engagement by the tires of the vehicles (such as forklift trucks) which can damage the joint. More specifically, wheels or tires with smaller diameters literally partially enter the joint as generally illustrated in FIG. 4 and engage the edge and/or inside wall of the elongated joint edge member such as member 40. This impact causes wear or damage to the rubber wheel or tire of the vehicle. This impact also loosens the engagement between the elongated joint edge member 40 and the slab 96. A series of these impacts can cause the concrete of the slab 96 behind or under the member 40 to break or crack, and possibly cause partial or complete disengagement of the elongated member 40 from slab 96. It should be appreciated that the same damage can happen to member 20 and slab 90 when the vehicles are moving in that direction.
Another problem with such wider joints is that as the joint becomes wider, the joint enables more contaminants (such as water) to enter the joint, which can damage the joint. While filler materials (such as elastomeric materials) can be used to fill these openings between the joints, as the concrete slabs continue to shrink, such filler materials often do not prevent contaminants from entering the joint.
One known attempt at solving these problems is generally illustrated in FIGS. 5, 6, and 7. This known joint edge assembly 110 includes two separate elongated joint edge members 120 and 140 temporarily held together by a plurality of connectors (not shown) which connect the elongated joint edge members 120 and 140 along their lengths during installation. This known joint edge assembly 110 further includes a plurality of anchors 122 that extend from the elongated joint edge member 120 into the region where the concrete of the first slab 190 is to be poured such that, upon hardening of the concrete slab 190, the anchors 122 are integrally cast within the body of the concrete slab 90. This known joint edge assembly 110 further includes a plurality of anchors 142 that extend from the elongated joint edge member 140 into the region where the concrete of the second slab 196 is to be poured such that, upon hardening of the concrete slab 196, the anchors 142 are integrally cast within the body of the concrete slab 196. The known joint edge assembly is positioned such that the ends of the slabs are aligned with the outer surfaces of the elongated joint edge members. A filler material is positioned in the joint between member 120 and 140 to prevent the wheels of the vehicles from entering the joint.
This known joint edge assembly 110 includes an elongated metal plate 180 attached to the bottom edge of the elongated joint member 120. FIG. 5 illustrates the joint edge assembly 110 after installation and immediately after the concrete is poured. This metal plate 180 is positioned to prevent the filler material above the plate from leaking into the portion of the joint below the metal plate 180.
FIG. 6 illustrates the joint edge assembly 110 after installation and after the concrete has started shrinking such that the elongated joint edge members 120 and 140 have separated and such that: (a) the distance between the facing sides of the concrete slabs 190 and 196 is X-A; and (b) the distance between the facing sides of the elongated joint edge members 120 and 140 is X-A. In various installations, X-A is approximately 9.525 millimeters (approximately 0.375 inches). As shown in FIG. 6, the metal plate 180 prevents the filler material above the plate from leaking into the portion of the joint below the metal plate 180.
FIG. 7 illustrates the joint edge assembly 110 after installation and after the concrete has shrunk further such that the elongated joint edge members 120 and 140 have separated to a greater extent than shown in FIG. 6 such that: (a) the distance between the facing sides of the concrete slabs 190 and 196 is X; and (b) the distance between the facing sides of the elongated joint edge members 120 and 140 is X. In various installations, X is approximately 20 millimeters (approximately 0.80 inches). As can be seen in FIG. 6, when the joint only opens to a limited extent (e.g., distance X-A), the metal plate 180 prevents the filler from entering the entire joint and specifically below the elongated joint edge members. However, as can be seen in FIG. 7, when the joint opens to a further extent (e.g., distance X), the metal plate 180 does not prevent the filler from entering the area of the joint below the metal plate 180. Additionally, the metal plate 180 cannot be made longer or substantially longer to prevent this filler leakage because that would cause weakness in the concrete slab 196. Thus, this known joint assembly works for certain sized joint openings, such as shown in FIG. 6, but does not work for larger sized joint openings, such as shown in FIG. 7.
Additionally, it is not practical or cost effective to solve this problem by making the elongated joint edge member 120, the elongated joint edge member 140, or the plate 180 wider because these members become too heavy and too costly.
Accordingly, there is a need for a joint forming apparatus and method that solves the above problems.